Australia's Jack Miller has won his first MotoGP race, triumphing in treacherous conditions at a restarted Dutch TT race in Assen where torrential rain forced the riders off the track after 14 laps.

With the restarted race on Sunday cut to 12 laps, the three leading riders - including seven-time Assen winner Valentino Rossi - all fell on the slick track, allowing Miller on his Honda to take a shock lead and hold on to pop a wheelie as he crossed the finish line.

The win for Miller's Estrella Galicia 0,0 Marc VDS team was the first MotoGP victory for an independent team since 2006.

Miller also became the first Australian to win in MotoGP since Casey Stoner's victory at the Phillip Island track in 2012.

Speaking after Sunday's race, which puts Miller 13th in the overall standings, the 21-year-old was clearly emotional.

"I don't know what to feel at the moment," CycleNews quoted Miller as saying.

"A lot of people have bad-mouthed us and everything like that and said that this project wouldn't work.

"I just hope that we've showed them wrong and that I can ride a bike, I'm not an idiot.

"Thank you to Honda for taking this risk on me. It's amazing."

Marc Marquez of Spain finished second to stretch his lead atop the world championship standings, while Scott Redding was third.

Jorge Lorenzo, second in the championship, carefully nursed his Yamaha around the wet track to finish 10th.

Before the race was stopped, riders largely managed to stay on board their bikes despite starting on a wet track, but after the restart the conditions caused carnage among the leaders.

The three riders on the front row for the 12-lap sprint - Andrea Dovizioso, Rossi and Danilo Petrucci - all fell and did not finish the race.

The Moto2 race was cut short by two laps because of the rain, with Takaaki Nakagami on his Honda profiting from the red flag to take his first win ahead of Johann Zarco of France, whose second place put him joint top in the season's standings with Alex Rins. Franco Morbidelli of Italy was third.

Earlier, in dry conditions, Francesco Bagnaia won his first Moto3 race in a photo finish and registered the first victory for his Aspar Mahindra team.